How IBM's Storage Controllers Keep Data Backups in the Right Order
A method for storage controllers to track and sequence data updates in a specific order, ensuring that remote backups remain consistent with the original data during a system failure.
Original patent title: “Cache queue entry linking for DASD record updates”
A method for storage controllers to track and sequence data updates in a specific order, ensuring that remote backups remain consistent with the original data during a system failure. Granted to International Business Machines Corp in 1997 with 13 claims and 145 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
This patent describes a way for a storage controller to manage updates to data stored on a disk. When an application updates multiple records, the controller creates a circular queue to track these changes. Each update is linked to the previous one in a backward chain, and a counter keeps track of how many updates are pending. This allows a data mover to read the updates in the exact order they occurred, which is critical for sending them to a remote site for disaster recovery without data corruption.
The gap
What does this patent NOT cover?
- Does not cover data storage systems that lack a cache-based circular queue structure.
- Does not cover methods of data transmission that do not require sequence-consistent ordering.
- Does not cover the specific hardware architecture of the host processor itself.
- Does not cover real-time data replication that occurs without a staging queue.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
By using a backward-linked chain within a circular queue, the system can efficiently track the sequence of updates without needing to constantly re-sort or re-index the entire list of changes as they arrive.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Enterprise storage area networks (SAN)
IBM z/OS remote copy services
Disaster recovery replication software
High-availability database transaction logs
Why it matters
The bigger picture
This technology is a foundational piece of enterprise disaster recovery. It ensures that if a primary data center fails, the remote backup site has an identical, chronological history of data changes. This prevents 'data skew' where a backup might reflect a later state of one file but an earlier state of another, which would crash databases.
Filed
March 31, 1995
Granted
October 28, 1997
Market context
Who's building on this
Companies in this space
IBM remains a primary player in this space, particularly within their mainframe and enterprise storage divisions. Modern cloud providers like AWS, Azure, and Google Cloud have built upon these fundamental concepts of asynchronous replication to power their own block storage and database backup services.
Market impact
This patent helped standardize how enterprise storage controllers handle asynchronous data replication. It enabled the growth of the disaster recovery industry by providing a reliable, hardware-level mechanism for maintaining data consistency across long distances, effectively becoming a requirement for mission-critical banking and government systems.
Claim 1 — Plain English
What this patent covers
This patent describes a way for a storage controller to manage updates to data stored on a disk. When an application updates multiple records, the controller creates a circular queue to track these changes. Each update is linked to the previous one in a backward chain, and a counter keeps track of how many updates are pending. This allows a data mover to read the updates in the exact order they occurred, which is critical for sending them to a remote site for disaster recovery without data corruption.
The clever bit
By using a backward-linked chain within a circular queue, the system can efficiently track the sequence of updates without needing to constantly re-sort or re-index the entire list of changes as they arrive.
What it does not cover
- Does not cover data storage systems that lack a cache-based circular queue structure.
- Does not cover methods of data transmission that do not require sequence-consistent ordering.
- Does not cover the specific hardware architecture of the host processor itself.
- Does not cover real-time data replication that occurs without a staging queue.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
9/20
Moderate scope
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$60K – $192K
Midpoint $120K · expired or expiring · industry ×1.6
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
13 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Legvold, V. J., Stanley, W. K., & Candelaria, S. K. (1997). How IBM's Storage Controllers Keep Data Backups in the Right Order (U.S. Patent No. 5,682,513). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/5682513/cache-queue-entry-linking-for-dasd-record-updates
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How IBM's Storage Controllers Keep Data Backups in the Right Order cover?
A method for storage controllers to track and sequence data updates in a specific order, ensuring that remote backups remain consistent with the original data during a system failure.
Who owns patent US 5682513?
International Business Machines Corp owns this patent, granted in 1997.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 5682513 cited by?
This patent has been cited by 145 later patents that build on its ideas.
What problem does this patent solve?
This technology is a foundational piece of enterprise disaster recovery. It ensures that if a primary data center fails, the remote backup site has an identical, chronological history of data changes. This prevents 'data skew' where a backup might reflect a later state of one file but an earlier state of another, which would crash databases.
What does this patent NOT cover?
Does not cover data storage systems that lack a cache-based circular queue structure.
Same assignee
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